Boost: Add e2e tests to concatenate JS/CSS

[dilirity]

Part of #33877

Proposed changes:

• Add helper plugin to enqueue assets used for testing;
• Add e2e tests for the Concatenate JS/CSS modules:
  • Meta isn't visible while the module is deactivated;
  • Concatenation doesn't happen when module is deactivated;
  • Meta is visible while the module is activated;
  • Concatenation happens when module is activated;
  • jQuery (JS) and admin-bar (CSS) aren't concatenated (since they are ignored by default) while module is activated.
• Update Boost CLI to support activating/deactivating concatenate JS/CSS;
• Update docker e2e test matrix to include tests (you can check the GH actions section to see the tests).

Other information:

• Have you written new tests for your changes, if applicable?
• Have you checked the E2E test CI results, and verified that your changes do not break them?
• Have you tested your changes on WordPress.com, if applicable (if so, you'll see a generated comment below with a script to run)?

Jetpack product discussion

n/a

Does this pull request change what data or activity we track or use?

no

Testing instructions:

• Run tests to see if everything is working as expected.

[github-actions]

Thank you for your PR!

When contributing to Jetpack, we have a few suggestions that can help us test and review your patch:

• ✅ Include a description of your PR changes.
  
• ✅ Add a "[Status]" label (In Progress, Needs Team Review, ...).
  
• ✅ Add testing instructions.
  
• ✅ Specify whether this PR includes any changes to data or privacy.
  
• ✅ Add changelog entries to affected projects
  

This comment will be updated as you work on your PR and make changes. If you think that some of those checks are not needed for your PR, please explain why you think so. Thanks for cooperation 🤖

---

The e2e test report can be found here. Please note that it can take a few minutes after the e2e tests checks are complete for the report to be available.

---

Once your PR is ready for review, check one last time that all required checks appearing at the bottom of this PR are passing or skipped.
Then, add the "[Status] Needs Team Review" label and ask someone from your team review the code. Once reviewed, it can then be merged.
If you need an extra review from someone familiar with the codebase, you can update the labels from "[Status] Needs Team Review" to "[Status] Needs Review", and in that case Jetpack Approvers will do a final review of your PR.

---

Boost plugin:

• Next scheduled release: May 7, 2024.
• Scheduled code freeze: April 29, 2024.

If you have any questions about the release process, please ask in the #jetpack-releases channel on Slack.

[haqadn]

This looks good. How much longer will the test be if both are combined? If not different by too much, maybe we can combine both? I think it requires workers to run each separately. But, I could be wrong.

[dilirity]

@haqadn thanks for the suggestion! I didn't check the timing, but it does make sense for the tests to be together.

Updated in d0359b3.

[haqadn]

LGTM